/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableMap.IteratorBasedImmutableMap;

import java.io.Serializable;
import java.util.EnumMap;
import java.util.Spliterator;
import java.util.function.BiConsumer;
import javax.annotation.CheckForNull;

/**
 * Implementation of {@link ImmutableMap} backed by a non-empty {@link java.util.EnumMap}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
final class ImmutableEnumMap<K extends Enum<K>, V> extends IteratorBasedImmutableMap<K, V>
{
    static <K extends Enum<K>, V> ImmutableMap<K, V> asImmutable(EnumMap<K, V> map)
    {
        switch (map.size())
        {
            case 0:
                return ImmutableMap.of();
            case 1:
                Entry<K, V> entry = Iterables.getOnlyElement(map.entrySet());
                return ImmutableMap.of(entry.getKey(), entry.getValue());
            default:
                return new ImmutableEnumMap<>(map);
        }
    }

    private final transient EnumMap<K, V> delegate;

    private ImmutableEnumMap(EnumMap<K, V> delegate)
    {
        this.delegate = delegate;
        checkArgument(!delegate.isEmpty());
    }

    @Override
    UnmodifiableIterator<K> keyIterator()
    {
        return Iterators.unmodifiableIterator(delegate.keySet().iterator());
    }

    @Override
    Spliterator<K> keySpliterator()
    {
        return delegate.keySet().spliterator();
    }

    @Override
    public int size()
    {
        return delegate.size();
    }

    @Override
    public boolean containsKey(@CheckForNull Object key)
    {
        return delegate.containsKey(key);
    }

    @Override
    @CheckForNull
    public V get(@CheckForNull Object key)
    {
        return delegate.get(key);
    }

    @Override
    public boolean equals(@CheckForNull Object object)
    {
        if (object == this)
        {
            return true;
        }
        if (object instanceof ImmutableEnumMap)
        {
            object = ((ImmutableEnumMap<?, ?>) object).delegate;
        }
        return delegate.equals(object);
    }

    @Override
    UnmodifiableIterator<Entry<K, V>> entryIterator()
    {
        return Maps.unmodifiableEntryIterator(delegate.entrySet().iterator());
    }

    @Override
    Spliterator<Entry<K, V>> entrySpliterator()
    {
        return CollectSpliterators.map(delegate.entrySet().spliterator(), Maps::unmodifiableEntry);
    }

    @Override
    public void forEach(BiConsumer<? super K, ? super V> action)
    {
        delegate.forEach(action);
    }

    @Override
    boolean isPartialView()
    {
        return false;
    }

    // All callers of the constructor are restricted to <K extends Enum<K>>.
    @Override
    Object writeReplace()
    {
        return new EnumSerializedForm<>(delegate);
    }

    /*
     * This class is used to serialize ImmutableEnumMap instances.
     */
    private static class EnumSerializedForm<K extends Enum<K>, V> implements Serializable
    {
        final EnumMap<K, V> delegate;

        EnumSerializedForm(EnumMap<K, V> delegate)
        {
            this.delegate = delegate;
        }

        Object readResolve()
        {
            return new ImmutableEnumMap<>(delegate);
        }

        private static final long serialVersionUID = 0;
    }
}
